This study compares DSM-III criteria in depressed children and adolescents (major depressive disorder) with biologic tests - the Dexamethasone Suppression Test (DST) and the Sleep Polysomnogram. This study will determine whether one or both of these measures in children aged eight to 18 distinguish between these diagnostic groups and normal controls. In addition, presence of depression will be evaluated using Weinberg criteria (standard and modified). Further, the relationship bewteen sympton severity and each biologic measure, as well as the effects of age and development on each test, will be studied. One hundred and twenty inpatients aged eight to 18 who meet DSM-III criteria for depression will be studied by two independent experienced clinicians. All patients will be evaluated for other disorders by DSM-III as well. Forty will be Tanner Stage 1, 40 Tanner Stage 2 and 3, and 40 Tanner Stage 4 and 5. Within each Tanner group, half (n = 20) will meet DSM-III criteria for major depression (unipolar type or bipolar depressed), whereas one half will meet criteria for dysthymia. Each patient will have three nights of sleep polysomnography followed by the DST. For Year Three we would expect to complete the proposed project by studying 30 patient subjects and 20 normal controls, selecting subjects to complete developmental and diagnostic groups.